It's very easy to use and kid-friendly--no ads or in-app purchases. The graphics that go with the text are beautiful. It has a lot of content--four levels and more in the works. The easiest levels are matching sentences and pictures. Then it's answering multiple-choice questions after reading a short text. It's a high quality app that works very nicely. I recommend it.

There are some really good apps of http://www.knowledgeadventure.com/ that I would recommend. When we were kids, we played with the CDs and now they have all of their resources on their website. Apart from free worksheets and printables, they also have some apps to get your kids to start reading. I would recommend that you don't get them hooked on to just technology though. Try to vary it with kinesthetic activities!